Tropical Depression GASTON

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TROPICAL DEPRESSION GASTON DISCUSSION NUMBER 5
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL AL092010
1100 AM AST THU SEP 02 2010
METEOSAT-9 VISIBLE AND INFRARED IMAGES SHOW THAT DEEP CONVECTION
ASSOCIATED WITH GASTON HAS DECREASED CONSIDERABLY AND IS LIMITED TO
A FRAGMENTED BAND OVER THE WESTERN AND NORTHERN PORTION OF THE
CIRCULATION. THE PIRATA PREDICTION AND RESEARCH BUOY 13008 LOCATED
ABOUT 80 N MI NORTH-NORTHEAST OF THE CENTER HAS BEEN ONLY AVERAGING
AROUND 17 KT DURING THE PAST 6 HOURS. DVORAK SATELLITE INTENSITY
ESTIMATES HAVE DECREASED TO 30 KT FROM BOTH TAFB AND SAB. BASED ON
THESE DATA...GASTON IS LOWERED TO TROPICAL DEPRESSION STATUS.
ALTHOUGH THE UPPER WIND PATTERN IS FORECAST TO BE CONDUCIVE FOR
STRENGTHENING...THE RATHER DRY AND STABLE THERMODYNAMIC ENVIRONMENT
DOMINATING THE EASTERN TROPICAL ATLANTIC SHOULD ONLY PERMIT SLOW
INTENSIFICATION. A NATIONAL SCIENCE FOUNDATION G-V AIRCRAFT IS
CURRENTLY ENROUTE ON A PREDICT RESEARCH MISSION TO SAMPLE THE
SURROUNDING ENVIRONMENT. THE OFFICIAL INTENSITY FORECAST FOLLOWS
THE ICON CONSENSUS MODEL...AND IS CLOSE TO THE SHIPS AND LGEM
MODELS AT DAYS 4 AND 5.
GASTON IS MOVING A LITTLE SLOWER AND TO THE RIGHT OF THE PREVIOUS
ADVISORY...AROUND 290/6...IN RESPONSE TO A MID- TO UPPER-LEVEL HIGH
AMPLITUDE TROUGH SITUATED ALONG 38W AND TO THE NORTH OF THE
TROPICAL CYCLONE. THE LARGE-SCALE MODELS AGREE ON A CONTINUED
SLOW WEST-NORTHWESTWARD MOTION WITHIN THE WEAK EASTERLY STEERING
FLOW INFLUENCED BY THE AFOREMENTIONED TROUGH THROUGH ABOUT 36
HOURS. AFTERWARDS...THE DYNAMICAL MODELS INDICATE THAT THE
SUBTROPICAL RIDGE WILL BUILD EASTWARD OVER THE CENTRAL ATLANTIC
THROUGH THE END OF THE PERIOD WHICH WOULD INFLUENCE GASTON TO MOVE
GENERALLY WESTWARD AT A SLIGHTLY QUICKER PACE. THE NHC OFFICIAL
FORECAST IS A LITTLE TO THE RIGHT OF THE PREVIOUS TRACK AND IS BASED
ON A COMPROMISE OF ALL OF THE DYNAMICAL MODELS.
FORECAST POSITIONS AND MAX WINDS
INITIAL 02/1500Z 14.0N 38.9W 30 KT
12HR VT 03/0000Z 14.1N 39.7W 30 KT
24HR VT 03/1200Z 14.3N 40.7W 35 KT
36HR VT 04/0000Z 14.5N 42.0W 45 KT
48HR VT 04/1200Z 14.7N 43.3W 50 KT
72HR VT 05/1200Z 15.0N 46.5W 60 KT
96HR VT 06/1200Z 15.5N 51.0W 70 KT
120HR VT 07/1200Z 16.0N 56.0W 85 KT
$$
FORECASTER ROBERTS/PASCH
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